Bonding pad structure and method for making same

ABSTRACT

An bonding pad structure has a passivation layer over a copper layer having a pad window to expose a portion of the copper layer, a barrier layer conformal to a profile of the pad window, and an aluminum pad located in the pad window. The metal layer can be an aluminum, aluminum alloy or aluminum dominated layer for providing a better adhesion property between the copper layer and the bonding wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of anapplication Ser. No. 09/595,496, filed Jun. 16, 2000, entitled“STRUCTURE OF METALLIZATION”, currently pending; which is a continuationof an application Ser. No. 09/100,769, filed Jun. 5, 1998, entitled“STRUCTURE OF METALLIZATION”, currently granted (U.S. Pat. No.6,084,304). All these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates in general to a metal interconnect, andmore specifically relates to a bonding pad structure interposed betweena copper layer and a bonding wire and a method for making the same.

[0004] 2. Description of Related Art

[0005] As the requirement on the complexity and precision of anintegrated circuit design keeps increasing in order to reduce thefeature size of a semiconductor device and increase the integration ofan integrated circuit, a semiconductor device has to contain more thantwo metal layers to achieve the fabrication of high-density metalinterconnects on a limited surface of a chip. Conventionally, aluminumis used as the material of a metal layer. However, as the design rulesof a semiconductor device get finer and higher, the requirements oflower resistivity and higher reliability increase as well. Since copperhas better conductivity and reliability than that of aluminum, copperhas become a new material used in the metal layers.

[0006]FIGS. 1A through 1C are the cross-sectional views showing aconventional metallization process. Referring to FIG. 1A, a number ofcopper interconnects are formed on a provided semiconductor substrate10, wherein the semiconductor substrate 10 has some pre-formed devices,such as a transistor (not shown). A multi-interconnect layer 12 is usedhere to represent all formed copper interconnects. A top copper layer 14is formed on the top of the multi-interconnect layer 12, and issurrounded by insulation layer 13.

[0007] Referring next to FIG. 1B, an insulation film 16 is deposited onthe top of the top copper layer 14, preferably by a chemical vapordeposition (CVD) process, wherein the insulation film includes SiN orSiON. Then, a passivation layer 18 is formed on top of the insulationfilm 16, wherein the passivation layer 18 includes borophosphosilicateglass (BPSG), phosphosilicate glass (PSG), spin-on glass (SOG), or otherdielectric materials. The preferable method for forming the passivationlayer 18 is also a CVD process.

[0008] Referring to FIG. 1C, the passivation 18 and the insulation film16 are patterned and etched through in sequence by a photolithographyprocess and an etching process for forming a pad window 19 to expose thetop copper layer 14.

[0009] The foregoing fabrication process for a top copper layer 14 tendsto manifest an occurrence of oxidation on the copper layer before orduring the next bonding process for connecting the top copper layer to abonding wire, because the top copper layer 14 is exposed to the air. Theoxidation of copper decreases the conductivity and the reliability of acopper interconnect, and further causes a short that might possiblydamage the whole integrated circuit.

SUMMARY OF THE INVENTION

[0010] According to the foregoing description, it is therefore anobjective of the invention to provide a bonding pad structure and methodfor making the same, for providing a better adhesion property betweenthe copper layer and the bonding wire.

[0011] According to the object mentioned above, the invention provides abonding pad structure. A passivation layer over a copper layer has a padwindow to expose a portion of the copper layer. A barrier layer isconformal to a profile of the pad window. And an aluminum pad is locatedin the pad window. Thereby, a better adhesion property is providedbetween the copper layer and the bonding wire.

[0012] In regard to the structure above, the invention provides a methodfor manufacturing an interconnection structure as follows. A substratewith a copper layer over the substrate is provided. A passivation layeris formed over the copper layer and then a pad window is formed withinthe passivation to expose a portion of the copper layer. A barrier layeris formed over the passivation layer and the pad window. After a portionof the barrier layer over the passivation layer is removed, a metallayer is formed over the passivation layer and filled in the pad window.A portion of the metal layer is removed to expose the passivation layer.Preferably, the metal layer is an aluminum layer. The portion of themetal layer can be removed by a chemical mechanical polishing (CMP)process, or an etching process.

[0013] The invention further provides another method for manufacturingan interconnection structure above as follows. First, a substrate with acopper layer over the substrate is provided, and a passivation layer isformed over the copper layer. A pad window within the passivation layeris formed to expose a portion of the copper layer. A barrier layer isformed over the passivation layer and the pad window and then a metallayer is formed over the barrier layer and filled in the pad window. Aportion of the metal layer and the barrier layer is removed to exposethe passivation layer. Preferably, the metal layer is an aluminum,aluminum alloy or aluminum dominated layer. The portion of the metallayer and the barrier layer can be removed by a chemical mechanicalpolishing (CMP) process, or an etching process.

[0014] The invention further provides a bonding pad structure. Apassivation layer is located over a copper layer having a pad window toexpose a portion of the copper layer. A barrier layer is conformal to aprofile of the pad window and extended along the surface of thepassivation layer from the pad window. And an aluminum pad is locatedover the barrier layer.

[0015] The invention also provides a method for manufacturing aninterconnection structure above, comprising steps as follows. Asubstrate with a copper layer over the substrate is provided. Apassivation layer is formed over the copper layer, and a pad window isformed within the passivation layer to expose a portion of the copperlayer. A barrier layer is then formed over the passivation layer and thepad window. A metal layer is formed over the barrier layer and filled inthe pad window. Next, a photoresist layer is formed over the metallayer, wherein the photoresist layer has a pattern covering the padwindow. A portion of the metal layer and the barrier layer are removedto expose the passivation layer. And the photoresist layer is removed.Preferably, the metal layer is an aluminum layer. The portion of themetal layer and the barrier layer can be removed by an etching process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] While the specification concludes with claims particularlypointing out and distinctly claiming the subject matter which isregarded as the invention, the objects and features of the invention andfurther objects, features and advantages thereof will be betterunderstood from the following description taken in connection with theaccompanying drawings in which:

[0017]FIGS. 1A through 1C are cross-sectional views showing aconventional metallization process;

[0018]FIGS. 2A through 2D are cross-sectional views showing ananti-oxidation process for the top copper layer in a preferredembodiment according to the invention;

[0019]FIGS. 3A through 3C are cross-sectional views showingmanufacturing process of the metallization according to the oneembodiment of the invention;

[0020]FIG. 3D schematically shows one bonding pad structure according tothe embodiment of the invention;

[0021]FIGS. 4A through 4B are cross-sectional views showing anothermanufacturing process for making the bonding pad structure shown in FIG.3D according to the embodiment of the invention;

[0022]FIGS. 5A through 5B are cross-sectional views showing amanufacturing process of the bonding pad structure according to anotherembodiment of the invention; and

[0023]FIG. 5C schematically shows another bonding pad structureaccording to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] In order to have a better adhesion property between a copperlayer and a bonding wire in subsequent process, the invention provides abonding pad structure using aluminum, aluminum alloy or aluminumdominated layer. Therefore, the adhesion and conductivity propertiesbetween the copper layer and the bonding wire are significantlyimproved. In general, the bonding wire is a gold wire and copper iseasily oxidized, causing a poor adhesion property between the copperlayer and the bonding wire. Therefore, an aluminum, aluminum alloy oraluminum dominated boding pad interposed between the copper layer andthe bonding wire can provide an excellent adhesion property withoutcopper oxidation issue. According to the invention, two preferablebonding pad structures and their corresponding manufacturing processesare disclosed.

[0025] First, referring to FIG. 3D, it schematically shows a bonding padstructure according to the invention. As shown, the bonding padstructure comprises a copper layer 22, a passivation layer 24 over thecopper layer having a pad window 25 to expose a portion of the copperlayer 22, a barrier layer 26 a conformal to a profile of the pad window25; and an aluminum pad 28 a located in the pad window. The aluminum pad28 a can provide a better adhesive property between the copper layer 22and the other conductive layer in subsequent process. Two exemplarymethods for making the structure in FIG. 3D are described in detail asfollows.

[0026] In addition, FIG. 5C schematically shows another bonding padstructure according to the invention. As shown, a copper layer 22 islocated within an insulating layer 27. A passivation layer 24 is locatedover the copper layer and has a pad window 25 to expose a portion of thecopper layer 22. A barrier layer 26 b is conformal to a profile of thepad window 25 and extended along the surface of the passivation layer 24from the pad window 25. An aluminum pad 32 a is located over the barrierlayer.

[0027]FIGS. 2A through 2D and FIGS. 3A through 3C schematically show amanufacturing process for making the bonding pad structure in FIG. 3D.Referring to FIG. 2A, a number of metal interconnects are formed on aprovided semiconductor substrate 20, wherein the semiconductor substratehas a number of pre-formed devices including metal layers (not shown)and transistors (not shown). A multi-interconnect layer 21 is used inthe diagram to represent the pre-formed metal interconnects. A copperlayer 22 is used to connect to a bonding wire.

[0028] In FIG. 2B, a cap layer 23 is formed on the copper layer 22. Thecap layer 23 comprises SiN or SiON. A preferable process to form the caplayer 23 comprises a CVD process. Then, a passivation layer 24 is formedover the cap layer 23. The passivation layer 24 comprises BPSG, PSG,SiN, doped oxide, undoped oxide or combination thereof, and a preferablemethod for forming the passivation layer 24 is a CVD process, forexample.

[0029] Referring to FIG. 2C, a photolithography process and an etchingprocess are performed to pattern and etch through the passivation layer24 and the cap layer 23 in sequence to form a pad window 25 to expose aportion of the copper layer 22.

[0030] Referring to FIG. 2D, a barrier layer 26, such as a thinconductive film 26, is formed over the passivation layer 24 and in thepad window 25, wherein the barrier layer 26 comprises material, such asaluminum (Al), tantalum (Ta), tantalum nitride (TaN), titanium nitride(TiN), and tungsten nitride (WN) thereof, mixtures thereof, combinationsthereof and alloys thereof The barrier layer 26 can protect the copperlayer 22 from exposure to the air. The method for forming the barrierlayer 26 comprises a sputtering process or a CVD process, for example.

[0031] Referring next to FIG. 3A, a portion of the barrier layer 26 overthe passivation layer 24 is removed to expose the passivation layer 24.For example, a chemical mechanical polishing (CMP) process can be used.Then, the exposed copper layer 22 and the sidewall of the pad window 25are covered by the barrier layer 26 a. In FIG. 3B, a metal layer 28 isformed over the passivation layer 24 and thus filled the pad window 25.For example, a CVD process or a sputtering process or any otherapplicable process in the art can be used to form the metal layer 28.Preferably, the metal layer 28 is an aluminum, aluminum alloy oraluminum dominated layer for preventing the copper oxidation issue.Referring to FIG. 3C, a planarization process is performed to remove aportion of the metal layer 28 and only the portion 28 a in the padwindow 25 is remained for serving as a bonding pad. In general, a CMP oran etching back process can be used to planarize the metal layer 28 andstops at the passivation layer 24.

[0032]FIGS. 2A through 2D and FIGS. 4A through 4B schematically showanother manufacturing process for making the bonding pad structure inFIG. 3D. The processes in FIGS. 2A through 2D are the same, andtherefore no redundant description is made herein after.

[0033] Referring next FIG. 4A, a metal layer 30 is formed over thepassivation layer 24 and thus filled the pad window 25. For example, aCVD process or a sputtering process or any other applicable process inthe art can be used to form the metal layer 30, and preferably, themetal layer 30 is an aluminum, aluminum alloy or aluminum dominatedlayer for providing a better adhesion property between the copper layer22 and the bonding wire. Referring to FIG. 4B, a planarization processis performed to remove a portion of the metal layer 30 and theunderlying barrier layer 26, and only the portion 30 a in the pad window25 is remained for serving as a bonding pad. In general, a CMP or anetching back process can be used to remove the metal layer 28 and theunderlying barrier layer 26 and stop at the passivation layer 24.

[0034]FIGS. 3A through 3C and FIG. 4A through 4B show two examples formaking the structure in FIG. 3D. It should be noticed that for thoseskilled in the art the structure in FIG. 3D can be made by modifying theprocesses shown in FIGS. 2A through 2D and FIGS. 3A through 3C, or inFIGS. 2A through 2D and FIGS. 4A through 4B.

[0035]FIGS. 2A through 2D and FIGS. 5A through 5B provide an exemplarymanufacturing process for making the bonding pad structure in FIG. 5C.The processes in FIGS. 2A through 2D are the same as the firstembodiment. No redundant description is made hereinafter.

[0036] Referring to FIG. 5A, after the process in FIG. 2D is finished, ametal layer 32 is formed over the barrier layer 26 and filled into thepad window 25, by depositing a metal layer using a CVD or a sputteringprocess or any other applicable process in the art. The metal layer 32comprises material of aluminum (Al), aluminum alloy or aluminumdominated layer, for example. A photoresist layer 34 is then formed overthe metal layer 32 at a position substantially corresponding thelocation above the pad window 25. For certain purposes, the width of thephotoresist layer 34 is larger the width of the pad window 25.

[0037] Referring to FIG. 5B, a portion of the metal layer 34 togetherwith the underlying barrier layer 26 are removed using the photoresistlayer 34 as a mask. In general, an etching process, such as a dry or wetetching process, can be used to complete the removals of the metal layer34 and the underlying barrier layer 26. The remaining barrier layer 26 bextends along the surface of the passivation layer 24, and a bonding pad32 a is formed to electrically connect the underlying copper layer 22.The bonding pad 32 a can provide a better adhesion property between thecopper layer 22 and the bonding wire.

[0038] It should be noticed that for those skilled in the art thestructure in FIG. 5C can be made by modifying the processes shown inFIGS. 2A through 2D and FIGS. 5A through 5B.

[0039] In addition to the forgoing aluminum bonding pad, a contact bumpstructure can be typically formed over the pad window for enhancedadhesion. The contact bump structure is substantially a round orcircular profile. Therefore, the invention can provide a chip with aball grad array (BGA) structure.

[0040] According to the foregoing, the metallization process and thebonding pad structure provided by the invention can prevent the copperlayer from oxidation, so that the conductivity remains excellent afterthe following bonding process, and the stability of device is improved.Furthermore, the aluminum bonding pad provides a better adhesionproperty between the copper layer and the bonding wire, and prevents thecopper oxidation issue. The process of the invention can be accomplishedby existing techniques, so no extra machines are required.

[0041] While the present invention has been described with a preferredembodiment, this description is not intended to limit our invention.Various modifications of the embodiment will be apparent to thoseskilled in the art. It is therefore contemplated that the appendedclaims will cover any such modifications or embodiments as fall withinthe true scope of the invention.

What claimed is:
 1. A boding pad structure, comprising: a copper layer;a passivation layer over the copper layer having a pad window to exposea portion of the copper layer; a barrier layer conformal to a profile ofthe pad window; and an aluminum pad located in the pad window.
 2. Thebonding pad structure of claim 1 , wherein the barrier layer is selectedfrom the group consisting of aluminum (Al), tantalum (Ta), tantalumnitride (TaN), titanium nitride (TiN), and tungsten nitride (WN),mixtures thereof, combinations thereof and alloys thereof.
 3. Thebonding pad structure of claim 1 , wherein the aluminum pad is analuminum, aluminum alloy or aluminum dominated layer.
 4. A bonding padstructure, comprising: a copper layer; a passivation layer over thecopper layer having a pad window to expose a portion of the copperlayer; a barrier layer conformal to a profile of the pad window andextended along the surface of the passivation layer from the pad window;and an aluminum pad located over the barrier layer.
 5. The bonding padstructure of claim 4 , wherein the barrier layer is selected from thegroup consisting of aluminum (Al), tantalum (Ta), tantalum nitride(TaN), titanium nitride (TiN), and tungsten nitride (WN), mixturesthereof, combinations thereof and alloys thereof.
 6. The bonding padstructure of claim 4 , wherein the aluminum pad is an aluminum, aluminumalloy or aluminum dominated layer.
 7. A method for manufacturing abonding pad structure, comprising steps of: providing a substrate with acopper layer over the substrate; forming a passivation layer over thecopper layer; forming a pad window within the passivation layer toexpose a portion of the copper layer; forming a barrier layer over thepassivation layer and the pad window; removing a portion of the barrierlayer over the passivation layer; forming a metal layer over thepassivation layer and filled in the pad window; and removing a portionof the metal layer to expose the passivation layer.
 8. The method ofclaim 7 , wherein the metal layer comprises an aluminum, aluminum alloyor aluminum dominated layer.
 9. The method of claim 7 , wherein theportion of the metal layer is removed by a chemical mechanical polishing(CMP) process.
 10. The method of claim 7 , wherein the portion of themetal layer is removed by an etching process.
 11. The method of claim 7, wherein the barrier layer is selected from the group consisting ofaluminum (Al), tantalum (Ta), tantalum nitride (TaN), titanium nitride(TiN), and tungsten nitride (WN), mixtures thereof, combinations thereofand alloys thereof.
 12. The method of claim 7 , wherein the passivationlayer comprises an doped oxide, an undoped oxide, nitride orcombinations thereof.
 13. The method of claim 7 , wherein the portion ofthe barrier layer is removed by a chemical mechanical polishing (CMP)process.
 14. A method for manufacturing a bonding pad structure,comprising steps of: providing a substrate with a copper layer over thesubstrate; forming a passivation layer over the copper layer; forming apad window within the passivation layer to expose a portion of thecopper layer; forming a barrier layer over the passivation layer and thepad window; forming a metal layer over the barrier layer and filled inthe pad window; and removing a portion of the metal layer and theunderlying barrier layer to expose the passivation layer.
 15. The methodof claim 14 , wherein the metal layer comprises an aluminum, aluminumalloy or aluminum dominated layer.
 16. The method of claim 14 , whereinthe portion of the metal layer and the underlying barrier layer areremoved by a chemical mechanical polishing (CMP) process.
 17. The methodof claim 14 , wherein the portion of the metal layer and the underlyingbarrier layer are removed by an etching process.
 18. The method of claim14 , wherein the barrier layer is selected from the group consisting ofaluminum (Al), tantalum (Ta), tantalum nitride (TaN), titanium nitride(TiN), and tungsten nitride (WN), mixtures thereof, combinations thereofand alloys thereof.
 19. The method of claim 13 , wherein the passivationlayer comprises an doped oxide, an undoped oxide, nitride orcombinations thereof.
 20. A method for manufacturing a bonding padstructure, comprising steps of: providing a substrate with a copperlayer over the substrate; forming a passivation layer over the copperlayer; forming a pad window within the passivation layer to expose aportion of the copper layer; forming a barrier layer over thepassivation layer and the pad window; forming a metal layer over thebarrier layer and filled in the pad window; and forming a photoresistlayer over the metal layer, wherein the photoresist layer has a patterncovering the pad window; removing a portion of the metal layer and thebarrier layer to expose the passivation layer; and removing thephotoresist layer.
 21. The method of claim 20 , wherein the metal layercomprises an aluminum, aluminum alloy or aluminum dominated layer. 22.The method of claim 20 , wherein the portion of the metal layer and theunderlying barrier layer are removed by an etching process.
 23. Themethod of claim 20 , wherein the barrier layer is selected from thegroup consisting of aluminum (Al), tantalum (Ta), tantalum nitride(TaN), titanium nitride (TiN), and tungsten nitride (WN), mixturesthereof, combinations thereof and alloys thereof.
 24. The method ofclaim 20 , wherein the passivation layer comprises an doped oxide, anundoped oxide, nitride or combinations thereof.